/*
 * Copyright (C) 2011 Markus Junginger, greenrobot (http://greenrobot.de)
 *
 * Licensed under the Apache License, Version 2.0 (the "License");
 * you may not use this file except in compliance with the License.
 * You may obtain a copy of the License at
 *
 *  http://www.apache.org/licenses/LICENSE-2.0
 *
 * Unless required by applicable law or agreed to in writing, software
 * distributed under the License is distributed on an "AS IS" BASIS,
 * WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
 * See the License for the specific language governing permissions and
 * limitations under the License.
 */

package com.mlizhi.base.dao;

import java.io.ByteArrayOutputStream;
import java.io.IOException;
import java.io.InputStream;
import java.io.OutputStream;

import android.content.Context;
import android.database.Cursor;
import android.database.DatabaseUtils;
import android.database.sqlite.SQLiteDatabase;

/** Database utils, for example to execute SQL scripts */
// TODO add unit tests
public class DbUtils {

public static void vacuum(SQLiteDatabase db) {
db.execSQL("VACUUM");
}

/**
 * Calls {@link #executeSqlScript(android.content.Context, android.database.sqlite.SQLiteDatabase, String, boolean)} with transactional set to true.
 * 
 * @return number of statements executed.
 */
public static int executeSqlScript(Context context, SQLiteDatabase db, String assetFilename) throws IOException {
return executeSqlScript(context, db, assetFilename, true);
}

/**
 * Executes the given SQL asset in the given database (SQL file should be UTF-8). The database file may contain
 * multiple SQL statements. Statements are split using a simple regular expression (something like
 * "semicolon before a line break"), not by analyzing the SQL syntax. This will work for many SQL files, but check
 * yours.
 * 
 * @return number of statements executed.
 */
public static int executeSqlScript(Context context, SQLiteDatabase db, String assetFilename, boolean transactional)
throws IOException {
byte[] bytes = readAsset(context, assetFilename);
String sql = new String(bytes, "UTF-8");
String[] lines = sql.split(";(\\s)*[\n\r]");
int count;
if (transactional) {
count = executeSqlStatementsInTx(db, lines);
} else {
count = executeSqlStatements(db, lines);
}
DaoLog.i("Executed " + count + " statements from SQL script '" + assetFilename + "'");
return count;
}

public static int executeSqlStatementsInTx(SQLiteDatabase db, String[] statements) {
db.beginTransaction();
try {
int count = executeSqlStatements(db, statements);
db.setTransactionSuccessful();
return count;
} finally {
db.endTransaction();
}
}

public static int executeSqlStatements(SQLiteDatabase db, String[] statements) {
int count = 0;
for (String line : statements) {
line = line.trim();
if (line.length() > 0) {
db.execSQL(line);
count++;
}
}
return count;
}

/**
 * Copies all available data from in to out without closing any stream.
 * 
 * @return number of bytes copied
 */
public static int copyAllBytes(InputStream in, OutputStream out) throws IOException {
int byteCount = 0;
byte[] buffer = new byte[4096];
while (true) {
int read = in.read(buffer);
if (read == -1) {
break;
}
out.write(buffer, 0, read);
byteCount += read;
}
return byteCount;
}

public static byte[] readAllBytes(InputStream in) throws IOException {
ByteArrayOutputStream out = new ByteArrayOutputStream();
copyAllBytes(in, out);
return out.toByteArray();
}

public static byte[] readAsset(Context context, String filename) throws IOException {
InputStream in = context.getResources().getAssets().open(filename);
try {
return readAllBytes(in);
} finally {
in.close();
}
}

public static void logTableDump(SQLiteDatabase db, String tablename) {
Cursor cursor = db.query(tablename, null, null, null, null, null, null);
try {
String dump = DatabaseUtils.dumpCursorToString(cursor);
DaoLog.d(dump);
} finally {
cursor.close();
}
}

}
